JPS6272597A - Oxide garnet single crystal - Google Patents

Abstract

PURPOSE:To provide a substrate single crystal for epitaxial growth of a garnet structural body of which the cations consist of 3 kinds of the oxides of Y, In and Al and which has good productivity. CONSTITUTION:The cations of the titled single crystal consist of 3 kinds of Y, In and Al and the crystal structure thereof is expressed by, for example, the formula Y3In2Al2O12. The crystal lattice constant thereof is 12.42-12.45Angstrom and the segregation coefft. is approximately 1. Since the single crystal has the above-mentioned crystal lattice constant and segregation coefft., this crystal is useful as the garnet substrate single crystal for the epitaxial growth of the bismuth-substd. magnetic garnet film expressed by the formula (BiRe)3(FeM)5O12 and since the crystal has excellent light transmittability, the crystal is useful as the substrate for an optical isolator as well. The single crystal is easily produced without twisting the single crystal in the pulling-up state by weighing respective raw materials to obtain the above-mentioned compsn. then housing the raw materials into a crucible and pulling up the crystal by a Czochralski process after heating and melting the crystal at 1,700-1,800 deg.C.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to a novel garnet single crystal for magnetic films that has not yet been published in any literature, particularly a magnetic film whose cations are composed of three oxides of Y, In, and AM. This invention relates to an oxide garnet crystal that is useful for bubble elements and magneto-optical elements.

[Conventional technology]

A magnetic film with a garnet structure made by epitaxially growing a rare earth iron-based magnetic garnet thin film can be used as a magnetic bubble element,
This epitaxially grown garnet structure is used as a magneto-optical element, but B
i.

Bismuth substitution magnetism consisting of cationic oxides of R, Fe, M (where R is Ca, Y, or one or more of the rare earth elements, M is a metal element that can be exchanged with iron such as Ga or A) It is said that the use of garnet film shows good results,
The use of this product is attracting attention. On the other hand, regarding the garnet substrate single crystal used to make the epitaxially grown layer having this garnet structure, l) the lattice constant of the crystal matches that of the magnetic film having the garnet structure within a range of about 0.01A;

2) The segregation coefficient of the elements constituting the crystal is required to be a value close to 1, but even though the lattice constant of the above-mentioned bismuth-substituted magnetic garnet film is 12.42 to 12.45A, In contrast, conventional single crystal substrates of this type, such as gadolinium gallium garnet (GGG) and neodymium
Since gallium garnet (NGO) has a lattice constant of 12.38 and 12.51 A, respectively, it cannot be said to be an optimal substrate for epitaxial growth of this bismuth-substituted magnetic garnet a, and various conventionally known substrates are used. Among the substrate single crystals, only samarium gallium garnet (SGG), which has a lattice constant of 12.43 A, is considered to be used for this purpose and has been put into practical use.

However, this SGG has the disadvantage that it is difficult to manufacture and has low productivity due to the phenomenon that the crystal is twisted when pulling a single crystal using the Czochralski method, so it is necessary to provide an alternative crystal in the substrate. It has been demanded.

[Structure of the invention]

The present invention relates to a crystal in a substrate for epitaxially growing a garnet structure, which does not have such disadvantages and has good productivity.
The present invention relates to an oxide garnet single crystal consisting of three types of Jl.

That is, 1. The present inventors used the crystal lattice constant 12 of the bismuth-substituted magnetic garnet film made of cationic oxides of (7) Bi, R, Fe, and M (R and M are the same as above) as the epitaxial growth layer described above. .42~12.45λ
As a result of various studies on garnet structures with lattice constants approximating
The oxide garnet single crystal consisting of three types has a lattice constant of 12.
．． 42λ, and the segregation coefficient of this material was approximately 1, and the crystal did not twist even when pulling a single crystal using the Czochralski method, and it could be easily pulled. The present invention was completed after confirming that it is possible to improve productivity.

The oxide garnet single crystal of the present invention is composed of three elements as cations: yttrium (Y), indium (In), and aluminum (A!L), and this crystal is cut from the crystal. After etching a wafer with hot phosphoric acid and measuring its lattice constant, we found 1
The lattice constant fi12.42 of a bismuth-substituted magnetic garnet film, for example, represented by the formula (B 1Re) (FeM)s 012, which is 2.419A and is made of the above-mentioned cationic oxides of Bi, R, Fe, and M.
~l 2.45A, and this segregation coefficient is Y from the gravimetric analysis value of this crystal.

Since both In and AM are considered to be 1.00-1.02, it is considered to be the optimal garnet substrate single crystal for epitaxially growing the above-mentioned bismuth fFi commutative garnet film. confirmed.

As mentioned above, the oxide garnet single crystal of the present invention is said to have three types of cations: Y, In, and All, and this crystal has Y and [
It is thought that In is placed at the al site and An is placed at the (d) site. But this is 2Y3I n21'
-130t2 is exemplified;
It is produced by putting a predetermined amount of No. 3 into a crucible and heating and melting it by high-frequency induction, and then pulling a single crystal from this melt using the Czochralski method.

That is, the present inventors have obtained, for example, the above formula Y3In2A
We investigated various methods for industrially producing garnet single crystals shown by fL30.2, and determined that the single crystal medium thorn method using the Czochralski method would be suitable for this purpose, and proceeded with research on these conditions. . The Y 2 O, In2O3, and AfL203 used here are preferably as pure as possible, and therefore, all of them preferably have a purity of 99.9% or more. These compounding ratios should be set to Y036-39 mol%, ■n20322-28 mol%, and AfL20336-39 mol%, since the target single crystal has the formula Y3■n2A9.3012, but there are some caveats. There is a need. After each of these is weighed, they are placed in a crucible and melted, and since the melting temperature of these is 1,700° C. or higher, this crucible may be made of iridium. The melting of this material can be carried out by high frequency induction according to the conventional method, and therefore, for example, 7
These are 1.700 using high frequency of KHz, 10KW.
What is necessary is just to heat it to ~1.800 degreeC and melt it.

The desired single crystal can be produced by pulling a single crystal from this melt using the Czochralski method, but the atmosphere in this case is 1 to 5% oxygen or 25 to 1% CO2 gas.
An atmosphere containing 00% nitrogen gas or argon gas may be used. In addition, the seed crystal used for pulling the single crystal has a formula of the same quality as the target single crystal, for example, Y3In2A sentence. 0.
2, but it may also be a single crystal of a garnet-type crystal such as gadolinium gallium garnet (GGG), and in this case, the pulling speed of the single crystal is 1 to 20 mm/hour. And it is sufficient.

Note that this single crystal pulling does not twist the single crystal during pulling unlike SGG, and this pulling can be performed extremely easily.After pulling, the single crystal is separated from the melt and cooled to achieve the desired purpose. A single crystal can be obtained.

For example, the formula Y3I n2 of the present invention thus obtained
An. As mentioned above, the single crystal represented by 012 has a crystal lattice constant of approximately 12.42A and a segregation coefficient of approximately 1, so the formula (B 1Re) '(F
It is said to be useful as a single crystal garnet substrate for epitaxially growing a bismuth l commutative garnet film shown by eM) 5012, but it also has excellent optical transparency, so it can also be used as a substrate for optical isolators. Considered useful.

Next, examples of the present invention will be described.

Example l In an iridium crucible with an outer diameter of 50 mm and a height of 50 mm,
Y2O3198, Ig (0.87 mol) In2 o3
162.4g (0.58 mol) and Al2O289
, 5g (0.88 mol) was weighed and charged, and nitrogen gas 9
8% and 2% oxygen gas by high frequency induction.
Heat it to 750℃ to melt it, and add a 5mm square G to this melt.
GG seed crystals are immersed and rotated at 10 rpm for 5 minutes.
When the single crystal was pulled at a speed of ~6 mm/hour, 86-3 g of transparent crystal was obtained.

Next, approximately 6 tg of samples were cut from the upper and lower parts of this crystal, and a quantitative analysis of each component metal source was performed using a high-frequency coupled induction plasma emission spectrometer, as shown in Table 1 below. This result confirmed that this material had a crystal structure expressed by the following formula %. When the segregation coefficients of each of these metals were calculated based on the results of this quantitative analysis, it was found that these is shown in Table 2,
It was confirmed that all of them were approximately l.

Table 2 also shows that for this crystal, a wafer with a thickness of inch was cut from the upper and lower parts of the crystal, etched with hot phosphoric acid, and then etched using a lattice constant precision measuring device APL2 (trade name manufactured by Rigaku Denki Co., Ltd.). When the lattice constants were measured by the method, they all showed a value of 12.419A.

Examples 2 to 4 The same treatment as in Example 1 was carried out except that the amount of metal oxide in Example 1 was changed to the amount shown in Table 3 below. are obtained, and these have the formula Y 3In2 A 13012 from the analysis results.
It had the crystal structure shown below.

Table 3 Example 5 Gold f! in Example 1 above! Melting of oxides.

The same process as in Example 1 was performed except that the gas atmosphere for pulling the single crystal from this melt was 50% nitrogen gas and 50% CO2 gas, and the same results as in Example 1 were obtained in this case as well. It was done.

Claims (1)

[Claims] 1. An oxide garnet single crystal containing three types of cations: Y, In, and Al. 2. The oxide garnet single crystal according to claim 1, which has a lattice constant in the range of 12.42 to 12.45 Å. 3. The oxide garnet single crystal according to claim 1, which has a crystal structure of Y_3In_2Al_3O_1_2.